Understanding on the kinetics of pyrolysis process of waste-printed circuit board (WPCB)

The loading of waste-printed circuit boards (WPCB) on environment increases year by year and that alerts for their appropriate and economical management. Pyrolysis is one of the promising modes being considered worldwide to circumvent this environmental problem. In this direction, a systematic study on thermal decomposition of WPCB was carried out using non-isothermal thermogravimetric (TG) data. The TG data were recorded from ambient temperature to 1073 K while heating powdered WPCB samples in five different heating rates in flowing N₂ atmosphere. The studies revealed that a large fraction of mass is lost in the temperature range of 573 to 673 K and slowly beyond this. The total mass loss is about 22-28%. The analysis of decomposition kinetic was carried out from these TG data using model-free iso-conversion expressions, like Kissinger, KAS, MKN, FWO and Friedman method. The activation energy and pre-exponential factors estimated were compared with the result obtained from model-based Coats-Redfern method. In addition, several models were also considered to construct Criado-master plots to compare with the experimental data. The evolved gas analyses by mass spectrometry revealed the release of water, CO₂ along with several type hydrocarbon species. The analyses of TG residue by powder XRD showed the presence of Cu along with non-crystalline materials which was supported by energy dispersive X-ray analysis (EDX) data. These results provide information on the chemical and physical processes involved in the decomposition of WPCB. The obtained information can be useful to optimize industrial set up for management of WPCB.